Change get_bucket to load only required bucket

[ibarria0]

As of now get_bucket() calls _get_buckets(). This tries to get all the buckets for the API KEY. The problem with this is that for example in my case I provide clients with IAM keys that can only access their particular bucket, not all the buckets in my company's account. The method fails because it tries to list all buckets and it does not have permission.

There is no reason for get_bucket to try to get all the buckets in the account.

I've made changes so that it fetches only the bucket supplied by conf.json.

[ibarria0]

I forgot to mention. This is an issue when upload to an s3 bucket and you only have access to the particular bucket, not every bucket of the account.

This is the case for when creating IAM users for clients that only have permissions for the client's particular bucket.

[ibarria0]

Bumpy mc bumperton with bumpersauce......

[ibarria0]

Ok, so... A bunch of tests fails because of the way the interaction with AWS is being tested. I'm gonna have to sit on this for a while.